Collaborative Research: Advanced Oxidation Processes for the Control of Iodinated Disinfection Byproducts in Drinking Water

About This Grant

Chemical oxidants such as chlorine are widely utilized as disinfectants to inactivate waterborne pathogens in conventional water treatment processes. However, chlorine can react with various background constituents in drinking water sources (e.g., natural organic matter, bromide, and iodide) to form undesirable and toxic disinfection byproducts (DBPs). Currently, the US EPA regulates the maximum contaminant levels (MCLs) of 11 DBPs in drinking water including 4 trihalomethanes (THMs), 5 haloacetic acids (HAAs), bromate (BrO-3), and chlorite (ClO2-). Unregulated iodinated DBPs (I-DBPs) are receiving increased attention as they are significantly more toxic than the regulated DBPs and can damage cells and DNA. I-DBPs are formed when chemical oxidants such as chlorine react with iodine and iodinated compounds (e.g., iodinated X-ray contrast media) during the disinfection of drinking water sources. Thus, the oxidation and conversion of iodine and iodinated compounds (ICs) to iodate (IO3–), a nontoxic source of iodine nutritional trace element, has emerged as a promising unit process to control and mitigate the formation of I-DBPs in water treatment systems. However, the ability of current water treatment processes to efficiently convert iodine and ICs to iodate suffer from several challenges including the concurrent oxidation of bromide to bromate and toxic brominated DBPs, and the incomplete transformation of iodine/ICs to iodate which can also lead to the formation of I-DBPs and other regulated DBPs in the final product water. The goal of this collaborative project is to explore the development of advanced oxidation processes (AOPs) and integrated treatment trains that can efficiently oxidize and convert iodine and ICs to iodate while minimizing and preventing the formation of toxic I-DBPs and regulated DBPs in the product drinking water. The successful completion of this project will benefit society through the development of new fundamental knowledge that could guide the design and deployment of more effective water treatment processes and systems for mitigating and eliminating and the formation of I-DBPs during water disinfection. Additional benefits to society will be achieved through student education and training including the mentoring of one graduate student and one undergraduate at the South Dakota School of Mines and Technology and one graduate student at South Dakota State University. Iodinated disinfection byproducts (I-DBPs) formed in drinking water treatment are highly toxic at low concentrations and have been found to be cytotoxic and genotoxic. Iodide (I–) and iodinated X-ray contrast media (ICM) are the two most common iodine sources that can react with disinfectants (e.g., chlorine and chloramines) to produce I-DBPs during drinking water treatment. The oxidation and conversion of iodine and iodinated compounds such as ICM to iodate (IO3–), a nontoxic source of iodine nutritional trace element, has emerged as promising unit process to control and mitigate the formation of I-DBPs in water treatment systems. The overarching goal of this project is to advance the fundamental science and engineering knowledge required to control emerging I-DBPs and regulated DBPs in drinking water treatment through careful selection and optimization of advanced oxidation processes (AOPs) and integration of the AOPs with conventional processes. The core guiding hypothesis of the proposed research is that the successful control of emerging I-DBPs and regulated DBPs in drinking water treatment systems would require the efficient oxidation and conversion of iodine species and iodinated compounds to iodate, the careful management of bromide formation, and the partial (decent) removal of NOM (Natural Organic Matter), a DBP precursor, prior to disinfection. The specific objectives of the research are to 1) to investigate the utilization of AOPs, including ferrate (Fe[VI]), ozone (O3), UV photolysis, and UV photolysis with O3, to optimize the oxidation of iodine and ICM to iodate; 2) investigate the integration of AOPs with conventional processes, including chlorination, and activated carbon sorption, to minimize the formation of both I-DBPs and regulated DBPs; and 3) develop analytical methods for measurement of iodine species and I-DBPs to unravel and quantify the transformation pathways of iodine and ICM to I-DBPs and total organic iodine. The successful completion of this project has the potential to advance the fundamental understanding of the reactivity and transformations of inorganic and organic iodine species/compounds by AOPs to guide the design and development of iodine source-specific treatment processes for effective mitigation of both I-DBPs and regulated DBPs in water treatment systems. To implement the education and training goals of this project, the Principal Investigators (PIs) propose to leverage existing programs at the South Dakota School of Mines and Technology (SDSMT) and South Dakota State University to recruit and mentor female students to work on the project. In addition, the PIs plan to interact and collaborate with drinking water treatment professionals to address water quality challenges in South Dakota, engage in local community outreach events, and collaborate with the SDSMT Ivanhoe International Center to engage and mentor international students from the African continent. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.